1. Field of the Invention
The present invention relates to a cooled reflective mirror apparatus which protects the reflection mirror from being overheated by the heat of a light source used in the reflection mirror. This type of reflection mirror apparatus employs a light source and is installed, for example, in an exposure device for printed circuit boards.
2. Description of the Prior Art
The light source of the exposure device uses a mercury lamp, which heats to high temperatures. Some light sources have their reflection mirror surfaces coated black to absorb the heat radiated from the lamp.
There are prior arts that are related to such an apparatus. Among them are U.S. Pat. No. 5,147,130 entitled "Cooling Liquid Recirculation System for Light Source Unit" and U.S. Pat. No. 5,150,253 entitled "Reflective Mirror Having Cooling Unit Attached."
The cooling structure of the prior art has heat dissipating fins formed at the back of the reflection mirror body and pipes installed between the fins for circulating cooling fluid. Overheating is suppressed by passing coolant through the piping and sending air from outside against the fins.
Such a cooling system has a cooling pipe for circulating the cooling fluid installed zigzag at the back of the reflective mirror facing the light source, at the back of a flat cold mirror, at the back of a curved cold mirror and also at the back of a light-transmitting mirror.
The cooling pipe is secured by a pipe holder, whose bottom surface is bonded with a silicon rubber of heat resisting elastic material and is fixed to a mounting member, thus forming a heat sink.
The outer surface of the cooling pipe in the heat sink is pressed against the back of the reflective mirror that transmits heat of infrared rays and the back of the cold mirror that reflects only ultraviolet rays. In this condition the cooling fluid is circulated through the cooling pipe.
Poor cooling capability of the pipe that passes the cooling liquid may result in deteriorated reflective mirror film over a long period of use. Also, air used for cooling may contaminate the printed circuit cards or films during the exposure process.